我使用 ffmpeg 库将帧编码为 .mp4 视频。该程序运行顺利，没有错误。但输出的 .mp4 视频无法播放。文件的属性甚至没有显示它是一个视频文件，没有任何视频流信息。
相关代码为：
const char* ouVideoFileName = "output.mp4";
AVCodecID ouCodec_id = CODEC_ID_H264;
但是如果我把它改成：
const char* ouVideoFileName = "output.avi";
AVCodecID ouCodec_id = CODEC_ID_H264;
.avi 视频可以正确播放。
.mp4 视频有什么问题？
【问题讨论】：
标签： ffmpeg mp4 video-encoding
您需要分享更多代码才能找到确切的问题。通常，一旦在输出文件名中指定了容器格式，就需要使用 av_guess_format 来获取输出格式。之后，您可以使用 av_find_encoder 建议 codec_id 你需要做这样的事情
AVFormatContext *m_outformat = NULL;
AVOutputFormat *outfmt = NULL;
std::string outfile = "clip_out.mp4";
outfmt = av_guess_format(NULL,outfile.c_str(),NULL);
if(outfmt == NULL)
{
ret = -1;
return ret;
}
else
{
m_outformat = avformat_alloc_context();
if(m_outformat)
{
m_outformat->oformat = outfmt;
_snprintf(m_outformat->filename, sizeof(m_outformat->filename), "%s", outfile.c_str());
}
else
{
ret = -1;
return ret;
}
}
AVCodec *out_vid_codec,*out_aud_codec;
out_vid_codec = out_aud_codec = NULL;
if(outfmt->video_codec != AV_CODEC_ID_NONE && m_in_vid_strm != NULL)
{
out_vid_codec = avcodec_find_encoder(outfmt->video_codec);
if(NULL == out_vid_codec)
{
PRINT_MSG("Could Not Find Vid Encoder")
ret = -1;
return ret;
}
else
{
PRINT_MSG("Found Out Vid Encoder ")
m_out_vid_strm = avformat_new_stream(m_outformat, out_vid_codec);
if(NULL == m_out_vid_strm)
{
PRINT_MSG("Failed to Allocate Output Vid Strm ")
ret = -1;
return ret;
}
else
{
PRINT_MSG("Allocated Video Stream ")
if(avcodec_copy_context(m_out_vid_strm->codec, m_informat->streams[m_in_vid_strm_idx]->codec) != 0)
{
PRINT_MSG("Failed to Copy Context ")
ret = -1;
return ret;
}
else
{
m_out_vid_strm->sample_aspect_ratio.den = m_out_vid_strm->codec->sample_aspect_ratio.den;
m_out_vid_strm->sample_aspect_ratio.num = m_in_vid_strm->codec->sample_aspect_ratio.num;
PRINT_MSG("Copied Context ")
m_out_vid_strm->codec->codec_id = m_in_vid_strm->codec->codec_id;
m_out_vid_strm->codec->time_base.num = 1;
m_out_vid_strm->codec->time_base.den = m_fps*(m_in_vid_strm->codec->ticks_per_frame);
m_out_vid_strm->time_base.num = 1;
m_out_vid_strm->time_base.den = 1000;
m_out_vid_strm->r_frame_rate.num = m_fps;
m_out_vid_strm->r_frame_rate.den = 1;
m_out_vid_strm->avg_frame_rate.den = 1;
m_out_vid_strm->avg_frame_rate.num = m_fps;
m_out_vid_strm->duration = (m_out_end_time - m_out_start_time)*1000;
}
}
}
}
if(outfmt->audio_codec != AV_CODEC_ID_NONE && m_in_aud_strm != NULL)
{
out_aud_codec = avcodec_find_encoder(outfmt->audio_codec);
if(NULL == out_aud_codec)
{
PRINT_MSG("Could Not Find Out Aud Encoder ")
ret = -1;
return ret;
}
else
{
PRINT_MSG("Found Out Aud Encoder ")
m_out_aud_strm = avformat_new_stream(m_outformat, out_aud_codec);
if(NULL == m_out_aud_strm)
{
PRINT_MSG("Failed to Allocate Out Vid Strm ")
ret = -1;
return ret;
}
else
{
if(avcodec_copy_context(m_out_aud_strm->codec, m_informat->streams[m_in_aud_strm_idx]->codec) != 0)
{
PRINT_MSG("Failed to Copy Context ")
ret = -1;
return ret;
}
else
{
PRINT_MSG("Copied Context ")
m_out_aud_strm->codec->codec_id = m_in_aud_strm->codec->codec_id;
m_out_aud_strm->codec->codec_tag = 0;
m_out_aud_strm->pts = m_in_aud_strm->pts;
m_out_aud_strm->duration = m_in_aud_strm->duration;
m_out_aud_strm->time_base.num = m_in_aud_strm->time_base.num;
m_out_aud_strm->time_base.den = m_in_aud_strm->time_base.den;
}
}
}
}
if (!(outfmt->flags & AVFMT_NOFILE))
{
if (avio_open2(&m_outformat->pb, outfile.c_str(), AVIO_FLAG_WRITE,NULL, NULL) < 0)
{
PRINT_VAL("Could Not Open File ", outfile)
ret = -1;
return ret;
}
}
/* Write the stream header, if any. */
if (avformat_write_header(m_outformat, NULL) < 0)
{
PRINT_VAL("Error Occurred While Writing Header ", outfile)
ret = -1;
return ret;
}
else
{
PRINT_MSG("Written Output header ")
m_init_done = true;
}
现在你可以开始帧的编码了
【讨论】：
我之前按照 FFmpeg 文档中的decode_encoding.c 示例。 后来我按照muxing.c的例子，现在可以了！
【讨论】：